Effect of Cutoff Radius on the Surface Tension of Nanoscale Bubbles

Abstract

Molecular dynamics simulations are performed to calculate the surface tension of bubbles formed in a metastable Lennard–Jones (LJ) argon fluid. The calculated normal and transverse pressure components are used to compute a surface tension which is compared to the surface tension computed from the Young–Laplace equation. Curvature effects on surface tension are investigated by performing various sized simulations ranging from 6912 to 256,000 LJ particles. The computed surface tension values differ depending on the calculation method for the smaller systems studied but the methods converge as the system size increases. Surface tension calculations on small bubbles may not be appropriate since the liquid farthest from the interface has yet to achieve the pressure profile of a homogeneous fluid. Density profiles, pressures, and calculated surface tensions are shown to have a strong dependence on the choice of the interaction cutoff radius. A cutoff radius of 8σ, significantly larger than that commonly used in the literature, is recommended for accurate calculations in liquid–vapor systems.